Conventional techniques for recording electrical or other physical events on strip chart recorders require either single or multiple trace recorders. Multiple trace recording is required if there are several parameters that must be recorded essentially simultaneously to obtain a condensed record which establishes the correct time relationship of the various parameters and events with respect to time and to each other. Conventional multitrace recorders may have either several meter movements, mounted side by side so that each one can write over a designated space on the chart paper, or there may be only a single recording meter movement which might be multiplexed to various input circuits, and simultaneously with the input multiplexing there might be a special multicolor ribbon that is mechanically multiplexed in synchronism so that each multiplexed input channel corresponds with a given color on the strip chart. There are also some mechanical arrangements where several recording meter movements are staggered in a unique manner so that each movement can write (with a different color) over the whole width of the chart paper without the individual pens interfering with each other. There are also recorders available with a mechanically multiplexed input selector switch which alternates between two separate input circuits. In order to identify one of the two input channels there is a mechanism that lifts the recorder pen for a moment away from the chart paper during the recording time of one of the channels. This then produces a broken trace in the recording of one channel.
Various techniques are used to write the recording traces. There are, for example, ink pens, multicolor ribbons (similar to a typewriter); heated pens which write on special heat sensitive chart paper; and impact recorders which utilize special pressure sensitive chart paper with a pressure bar that periodically impacts the pointer of a meter movement or the recorder against the sensitive paper surface. This latter technique produces essentially a dot pattern. However, if the chart paper moves slowly, it will cause the individual dots to flow into each other so that they appear as a continuous trace. This last type of recording mechanism is very popular because it is relatively inexpensive as compared to other techniques. However, since it uses pressure sensitive chart paper, it is essentially limited to single channel recording for a given meter movement. Of course, there are multiple trace impact recorders available where several movements are mounted side by side. All multiple trace recorders are very expensive, and they require extensive repair and maintenance at frequent intervals. Consequently, there is a need for new recording techniques of multiple trace recordings on single movement strip chart recorders.